Rock crusher



Oct. 16, 1962 c. E. HERMANN ROCK CRUSHER Filed Feb. 23, 1960 3 Sheets-Sheet 1 Oct. 16, 196 c. E. HERMANN 3,058,676

ROCK CRUSHER Filed Feb. 23, 1960 5 Sheets-Sheet 2 Oct. 16, 1962 c. E. HERMANN 3,058,676

ROCK CRUSHER Filed Feb. 23, 1960 3 Sheets-Sheet 3 FIG 3 United States Patent Ofitice 3,058,676 Patented Oct. 16, 1962 3,058,676 ROCK CRUSHER Charles E. Hermann, 4382 Westminister Place, St. Louis, Mo. Filed Feb. 23, 1960, Ser. No. 10,412 8 Claims. (Cl. 241186) This invention concerns equipment for crushing frangible materials such as rock, brittle chemicals, aggregates or the like, and more particularly equipment of the type known as an impact mill, this term being understood to encompass any mill in which the material to the crushed is struck by revolving hammers or impeller bars. Although its advantages are most efiiciently utilized in the pure impact type of mill, its teachings are equally applicable to the type of mill which combines an initial impact action with a subsequent grinding action.

In essence, the invention rests on the discovery that if the initial crushing of the material takes place by impelling the material against a flat, solid breaker plate extending from a level substantially above the crest of the hammer circle described by the tips of the rotating impeller hammers, to a level approximately even with the impeller shaft, then the particle size of the finished product can be adjusted within :a wide range by a relatively slight change in the angularity of the breaker plate surface with respect to a horizontal plane. In the past, it had been thought that the particle size could effectively be changed in an impact mill only by changing the rotor velocity, the number of hammers, the cross-sectional configuration of the breaker plate, or a combination of these. Each of these adjustments required at least a shutdown of the equipment, and more often the use of expensive hoisting machinery and skilled labor. With this invention, however, the breaker plate can easily be moved while the crusher is running by means of a two-way hydraulic jack, so that adjustment of the particle size can be continuously controlled by the mere turning of a valve, or even by remote control if desired. Elimination of the necessity of providing a variable speed drive permits coupling the drive motor directly to the drive shaft of the mill, with a resulting substantial saving in initial and maintenance costs.

The flat construction of the breaker plate of this invention has two other advantages: first, it avoids the danger of rock jams caused by rapidly propelling a large number of rock fragments in criss-ctrossing paths resulting from the zig-zag cross-section of conventional breaker plates, which cause fragments to momentarily accumulate in the recesses of the breaker plate; and second, it avoids ricocheting of the rock which results in unnecessary wear of the equipment. Ricocheting of the rock fragments is avoided by so positioning the plates that the rock, after impact, follows a curved trajectory generally clear of the hammer circle and into the discharge opening. The reduced probability of impact due to the reduction of ricocheting is compensated by an increase in the length of the active faces of the hammers.

In addition to the overall sizing effect of the upper or primary breaker plate, I have discovered that the proportion of fine particles to coarse particles can be controlled in the mill of this invention by providing a lower or secondary breaker plate of flat, solid configuration immediately below the upper breaker plate. Optirnurn control is achieved by mounting the lower breaker plate so that its impact surface forms a constant angle with a horizontal plane but can be moved horizontally toward and away from the hammer circle.

It is therefore an object of the invention to provide a hammer mill in which the size of the product is controlled by adjusting the angularity of a flat primary breaker plate.

It is another object of the invention to provide a hammer mill in which the proportion of fine to coarse product can be controlled by adjusting the position of a fiat secondary breaker plate.

It is still another object of the invention to provide a hammer mill having sufficiently long hammers to impel rock fast enough to accomplish its fracture without the necessity of causing the rock to ricochet into the hammer circle for repeated impact.

It is a still further object of this invention to provide an adjustable feed chute having provisions for keeping uncrushed rock from getting caught between the outside hammers and the casing of the mill.

These and other advantages of my improved impact mill will become apparent from the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a transverse vertical section of my improved hammer mill;

FIGURE 2 is a longitudinal section along line 22 of FIGURE 1;

FIGURE 3 is a detail view of the breaker plate adjustment mechanism; and

FIGURE 4 is a detail view of a hammer.

In general, my improved mill consists of a breaking chamber in the center of which is located a hammer drum on which a large number of heavy steel hammers are pivotally suspended. A feed chute is provided in the top of the casing immediately above the hammer drum, and large rocks to be broken up are introduced into the breaking chamber through this feed chute. Rapid rotation is imparted to the hammer drum by appropriate machinery so that the rocks falling down the feed chute are eventually hit by the rapidly revolving hammers and are thrown violently against an upper breaker plate, where they disintegrate under the force of the impact.

The kinetic energy of the rock impelled by the hammer is largely absorbed by the fracturing stress when the rock is crushed against the breaker plate. Hence, the crushed particies will ricochet only slightly, and, due to their own weight, will fall in a predominantly vertical trajectory toward the discharge opening. Since the upper breaker plate is arranged in such a manner that its lower half does not overlie the hammer circle, a substantial portion of the fractured rook particles will fall clear of the hammers. A few uncrushed rock particles ricochet back toward the hammer drum. Before they hit the drum, they are again hit by the revolving hammers and crushed either by impinging upon a lower breaker plate or by being subjected to a grinding action between the hammers and appropriate grate bars, if such are provided. If a lower breaker plate is provided and is positioned below the upper breaker plate as shown in the drawings, the particles falling downward from the upper breaker plate will impact upon the lower breaker plate and will become further crushed thereby. Most of the breakage in my mill occurs on the first pass, thus reducing power consumption and increasing the capacity per unit of time of the bill.

The crushed rock particles fall toward the bottom of the casing by gravity andleave the breaking chamber through an opening in the bottom thereof. After leaving the breaking chamber, the crushed rock is then conveyed to sizing equipment, and provisions are made for returning any over-sized rock back to the feed chute of the breaking chamber for another trip through the mill. In order to reduce wear and to utilize both faces of the hammers, the hammer drum is made reversible, i.e., it may rotate either clockwise or counter-clockwise. A duplicate set of breaker plates are arranged on the side of the breaking chamber opposite that on which the firstmentioned breake plates are located. Consequently, the a right-hand breaker plates in FIG. 1 will be used if the drum turns clockwise, whereas the left-hand set Will be used when the drum turns counter-clockwise. Inasmuch as the size of the rock particles delivered by the mill depends in large measure on the position of the upper breaker plate relative to the hammers, means are provided in my impact mill for adjusting the position of the upper breaker plates toward or away from the hammer drum by pivotally moving them about a bearing at their top by means of two-way hydraulic jacks or other convenient means.

The lower breaker plate is arranged to be moved horizontally toward and away from the hammer circle. The surface of the lower breaker plate forms a constant angle with the horizontal throughout its range of adjustments. Movement of the lower breaker plate toward the hammer circle increases the percentage of fine particles in the finished product, while moving the plate away from the hammer circle makes the product more evenly distributed among the various sizes, the range of which is primarily determined by the position of the upper breaker plate. In general, the position of the lower breaker plate follows that of the upper, i.e., its normal position is directly below the center of the upper plate. From that normal position, the lower plate is then moved closer to the hammer circle as necessary to achieve the desired proportion of sizes in the finished product.

The crushing of rock in an impact mill is usually accompanied by the formation of considerable dust. In a conventional mill, this dust is drawn around the hammer circle by the hammers and is thrown up into the feed chute where it accumulates and finally escapes into the atmosphere, creating a considerable dust nuisance. At the same time, the air currents set up by the movement of relatively heavy dust particles upward toward the feed chute interfere with the dropping of the uncrushed rocks and prevent them from being hit by the hammers at an optimum angle. In order to prevent this interference of the dust with the feed, I have provided a deflector plate and a recirculating conduit by which the dust is deflected upward and out of the breaking chamber just before reaching the feed chute. The dust is then conducted through an upwardly extending conduit which is curved at its top so as to reverse the direction of flow of the dust and is directed downward into the feed chute in a direction substantially equal to the direction of feed, thus eliminating air current interference and dust emission from the feed chute.

In order to reduce the inherent inertia of the rotating parts and the Wear of the hammers, while at the same time increasing the effectiveness of the hammer blow, I provide a very small hammer drum and suspend therefrom long hammers which present long impact faces to the incoming rock. In this respect, I have found that an unexpectedly good increase in capacity per hour, coupled with a considerable reduction in drive power, can be achieved by making the hammer faces of a length of at least 40% of the radius of the hammer circle, i.e. reducing the radius of the hammer-supporting discs to 60% or less of the hammer circle radius.

The theoretical minimum length L of the impact faces of the hammers can be computed by determining the distance through which a rock can fall during the interval of time necessary for the impeller drum to turn through the are which separates one hammer bank from the next. Thus, if the length L of the impact faces of the hammers is equal or greater than that distance, a rock just missing a hammer in its fall is bound to be struck by the next hammer before it can fall far enough to clear the impact face of the next hammer. Mathematically, this relationship can be expressed with good approximation by the formula wherein L=length of hammer faces in cm.

g=gravity acceleration constant (980 cm./scc.

s=free-fall distance of rock from feed conveyor to perimeter of hammer circle in cm.

w=revolutions of the hammer per second n=number of rows of hammers on the hammer drum For example, if the distance from the end of the feed conveyor through the feed chute to the perimeter of the hammer drum is six feet (182.8 cm.), and the drum turns at 1200 r.p.m., in the embodiment shown in the drawings, the above formula shows that the minimum hammer face length is or about four inches.

However, hammers constructed strictly in accordance with the above formula have a tendency to wear rapidly at their upper edges. I have discovered that by increasing the length of the hammer faces to from two to four times the calculated minimum length, I obtain a distribution of the wear over the entire hammer surface coupled with a great reduction of the wear at the upper edges of the hammers. This distribution of the wear has been empirically found to increase the life of the hammers as much as fivefold over the average life of hammers having only a minimum length.

As appears from FIG. 2, the sides of the feed chute of my mill are inclined inwardly so as to throw any incoming rock toward the center of the hammer drum. This arrangement prevents uncrushed rocks from becoming caught between the outside hammers and the casing of the breaking chamber, thus preventing serious interference with the motion of the hammer drum and injury to the machine. Inasmuch as the motion of the rock varies with the size and type of rock fed into the machine, I prefer to make the inward inclination of the sides of the feed chute variable. Thus, it is possible to set the inclination individually for each type of feed in such a manner that catching of rocks is prevented, but that the maximum possible width of the hammer drum is effectively utilized.

In addition, in View of the fact that some rocks may nevertheless get caught between the end hammers and the casing, I may prevent them from being destructively dragged around for many revolutions of the hammer drum by providing a liner, on the inside side walls of the casing, which is thicker in the portion of the casing lying above the axis of the drive shaft than in the portion below it. Hence, if a rock gets caught between a hammer and the top portion of the liner, it will be drawn around the hammer drum until it reaches the bottom portion of the liner, where the clearance between the hammer and the liner becomes suflicient for the rock to come free and be discharged.

In order to reduce twisting strain on the drive shaft, I may provide two fly Wheels, one located on each end of the drive shaft. This arrangement is useful when particularly large rocks have to be crushed, as such large rocks impart a considerable reactive force to the hammers in opposition to movement of the drum.

Referring now to FIGS. 1 and 2, my improved impact mill is generally shown therein at 10. The mill consists of a steel casing 12, the upper portions 14 of which may be latched to each side of a fixed vertical center portion 15 at 14a. The casing 12 and upper portion 14 can be pivoted outward about the pivot pins 13 making breaker plates 16 and the hammer drum 18 easily accessible. The hammer drum 18 is mounted on a drive shaft 24 to which are keyed a series of discs 26. In accordance with one aspect of this invention, the discs 26 are made of relatively thin, light material to reduce the inertia of the rotating parts. Hammer bolt holes 27 are provided in discs 26 at points sufliciently remote from the shaft 24 that the hammer bolts 28 extending therethrough will clear the bearings 36 when they are pulled out in order, for example, to replace the hammers. Inasmuch as the thin lightweight discs 26 are not strong enough to withstand the wear of hammer bolts 28 against holes 27', inserts 29 of a very hard material are inserted in the holes 27 to interpose a wear-resistant barrier between the hammer bolts 28 and the discs 26. The hammer bolts 28 loosely support the inner ends of hammers 30 to allow pivotal movement of the hammers 30 with respect to the discs 26. The discs 26 are kept appropriately separated by spacers 32. A pair of fly wheels 34 are mounted on each end of shaft 24, the shaft 24 being supported in bearings 36 located inwardly of the fly wheels 34 and supported by hearing supports 38. Power is applied to the drive shaft 24 by any convenient impelling means such as a motor (not shown). A discharge opening 40 is provided at the bottom of the breaking chamber for the egress of the crushed particles. A feed shute 42 is arranged at the top of the casing 12 directly above the center of the drum 18.

Openings 44 in the top of the casing on each side of the feed chute 42 lead to conduits 46 having a vertical portion 48 leading out of the breaking chamber and an oblique portion 50 leading downward into the feed chute 42 through openings 52. Deflector plates 54, hinged to the top of casing 12, can be operated by any convenient crank-and-gear-type operating means 55 (FIG. 2) to either close the opening 44 with which they are associated, or to depend downward toward the hammer circle so as to present a deflecting barrier to dust swirled around by the hammers for deflecting the dust into conduit 46 through opening 44.

Individual adjustment of the breaker plates 16 to obtain the proper size range of the finished product may be achieved by the use of two-ended hydraulic cylinders 56 (FIG. 3) whose pistons 51 are mechanically linked by connecting members 53 to pusher bars 58 which in turn extend into housing 12 through dust seals 57 and are hingedly aflixed at 59 to the lower end of breaker plate 16. The cylinders 56 associated with the upper breaking plate are hingedly attached to both the frame of the mill and the connecting members 53. 'Plates 16 is hinged on a transverse shaft 60, so that operation of the pusher bars 58 causes breaker plate 16 to pivot about shaft 60 so as to vary its angularity.

Lower plate 22 is equipped with a plurality of parallel pusher bars 58 tied together at 61 and operated by an other two-way hydraulic cylinder 56. The lower end of plate 22 is equipped with a shoe 62 riding on a rail 63. Thus, when tie bar 61 is moved back and forth by its cylinder 56, the angularity of plate 22 will remain constant while it moves toward and away from the hammer circle.

Locking means 64, consisting of plates 66 having apertures 63 cooperating with corresponding apertures 70 in the pusher bars 58, are used on all pusher bars 58 to lock the breaker plates in place after they have been appropriately adjusted (FIG. 3), in order to prevent gradual misadjustment of the breaker plates due to vibration or leakage in cylinders 56. This is accomplished by inserting a pin 72 through corresponding ones of the apertures 68 and 70, which are in a straight line on the mechanism associated with lower plate 22, but in a curved line on the mechanism associated with upper plate 16, because during movement of plate 16, the axes of its pusher bars 58 pivot about the center of dust seal 57.

Lateral deflectors 74 (FIG. 2) hinged at 73 and adjustable by a crank-and-gear device 75, are mounted at the bottom end of feed chute 42 for the purpose of directing the rock falling through the feed chute 42 toward the center of the breaking chamber, whereby the uncrushed rocks are prevented from getting caught between the outside hammers 76 and the casing 12. Liners 20 having a thick upper portion 19 and a thin lower portion 21 are provided to quickly discharge those rocks that do get caught, as explained hereinabove.

In operation, if it is desired, for example, to run the mill in a clockwise direction in FIG. 1, the lefthand deflector 54 is lowered and the right-hand deflector 54 is raised. In this condition, the right-hand opening 44 is closed off, and the left-hand Opening 44 is ready to receive dust deflected by the left-hand deflector plate 54. The right-hand breaker plate 16 is then adjusted in accordance with the size range of the end product desired, i.e., it is moved to the right for a generally coarser product, to the left for a generally finer product. In order to prevent ricocheting of fragments toward the feed chute, the upper breaker plate 16 is so positioned that it cannot be adjusted so that the angle a (FIG. 1) becomes obtuse, a being the maximum angle at which a rock, falling down the extreme left side of chute 42 and thrown by a hammer into a trajectory 77 tangential to the hammer circle 79, can hit the breaker plate 16.

Next, the lower right-hand breaker plate 22 is moved into position generally below the plate 16, and more or less close to the hammer drum depending on the proportion of fines desired in the output. Moving plate 22 closer to the hammer drum will increase the percentage of fine fragments in the output while moving it away from the drum will decrease the percentage of fines. At the same time, the total through-put of the machine can. be adjusted to some degree, as the total through-put is Somewhat less for a generally fine product or a high-percentage of fines in the product than for a generally coarse product or a low percentage of fines in the product. Care should be taken, however, that the lower breaker plate not be moved closer to the hammer circle than the upper plate, particularly when the plates are close to the hammer circle, as jamming of the mill may result.

Finally, the screws 75 are used to adjust the sloping sides 74 of the feed chute 42 to obtain the optimum distribution of the incoming rock along the hammer drum, in view of the size and composition of the material to be crushed.

Rapid rotation is now imparted to the drum 18, which will cause the hammers 30 to assume a radial position due to the resulting centrifugal force. If a rock is now fed into the mill through the feed chute 42, the rock will be struck in mid-air by the outer end of a face 78 of a hammer 30 (if the mill were turning in the other direction, the rock would be struck by the face 80 of the hammer 30). The impact of the face 78 against the incoming rock causes it to be thrown to the right against the unyielding breaker plate 16. The impact of the rock against breaker plate 16 coupled with the previous impact of the hammer against the rock is suflicient to crumble or crush the rock into fragments, the size of which depends on the relative position of the breaker plate and the hammers. Some of the few unbroken fragments of rock now ricochet back toward the hammer drum and are again hit by the faces 78 of hammers 30 which this time throw the rock particles against breaker plate 22 where a minor part of the crushing is usually achieved. The rock particles thereupon fall downward toward the opening 40 from which they are discharged onto a conveyor belt (not shown) which conveys them to the sizing machine. Dust particles are not at first discharged through the opening 40 but are drawn along by the strong revolving air currents set up by the rapidly revolving hammers. The centrifugal force acting on the dust particles eventually draws them away from the hammer circle and toward the left-hand breaker plate 16 and feed chute 42. However, deflector plate 54 prevents movement of the dust particles toward the feed chute and instead directs them into opening 44 from whence they travel upward to the top of conduit 46. At the top of conduit 46, the direction of motion is reversed and the dust particles travel downward through the portion 50 of conduit 46, and through opening 52 into feed chute 42 where they become mixed with the incoming rock and descend back into the breaking chamber.

Eventually, the inside of the casing becomes saturated with dust, which will then condense and be discharged onto the discharge conveyor through the opening 40.

It will be seen from the above description that I have provided a clean, efficient, and economical impact mill in which both the size range of the product and its percentage content of fines can be readily adjusted by a simple adjustment of the breaker plates without disturbing the speed setting of the hammer drum, or any other parts of the machine.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A materials crusher comprising a breaking chamber, revolving hammer means positioned within said breaking chamber, the tips of said hammer means describing a hammer circle during revolution of said hammer means, a continuous substantially flat breaker plate extending laterally of said hammer circle outwardly from a level above the highest point of said hammer circle to a level substantially even with the center of said hammer circle, the size to which material dropped into the crusher will be reduced immediately upon striking said breaker plate being dependent upon the angle of inclination of said breaker plate, and means for varying the angle of inclination of said breaker plate to control the size of the material produced by the impact of the material on the breaker plate, said last-named means including means for pivoting said breaker plate adjacent its upper end.

2. A materials crusher as set forth in claim 1, which further includes a pusher member attached near the lower end of said plate and extends to the outside of said breaking chamber, means for imparting movement to said pusher member, and locking means for releasably holding said pusher member against movement.

3. A materials crusher comprising a breaking chamber, revolving hammer means positioned within said breaking chamber, the tips of said hammer means describing a hammer circle during revolution of said hammer means, a continuous substantially flat upper breaker plate positioned in the upper half of said breaking chamber adjacent said hammer means and extending laterally of said hammer circle outwardly from a level above the highest point of said hammer circle to a level substantially even with the center of said hammer circle, means for pivoting said breaker plate adjacent its upper end whereby the angle of inclination of said breaker plate may be varied to control the size of the material produced by the impact of the material on the breaker plate, and a lower substantially fiat breaker plate extending through substantially the entire height of the lower half of said breaking chamber beneath said upper breaker plate.

4. A materials crusher as set forth in claim 1 wherein said hammer means comprises a hammer bolt, a plurality of hammers pivotally mounted on said hammer bolt, a rotating shaft, a plurality of lightweight support members attached to said rotating shaft and extending radially therefrom, said hammer bolt being supported in apertures formed in said support members, and inserts interposed in said apertures between said support members and said hammer bolt, said inserts being formed of a material considerably harder than the material of said support members.

5. A materials crusher comprising a housing defining a breaking chamber, a feed chute, a pair of breaker plates, operating mechanism for moving each of said breaker plates, rotatable hammers mounted in said breaking chamber, said housing comprising a fixed central portion supporting said feed chute, and a pair of pivotable casings, each of said casings comprising an end wall, two side Walls, and an upper portion, each of said casings supporting one of said breaker plates and operating mechanism associated therewith and being swingable away from said rotatable hammers so as to bring said breaker plate into a position where it is easily accessible for servicing and does not impede access to other mechanism located interiorly of said breaking chamber.

6. A materials crusher as set forth in claim 1, which further includes means associated with the walls of said breaking chamber perpendicular to the axis of revolution of said hammer means for reducing the axial dimension of said breaking chamber in the upper half of said hammer circle as compared to the axial dimension of said breaking chamber in the lower half of said hammer circle.

7. A materials crusher as set forth in claim 4, further comprising means mounting said shaft for rotation in a reverse direction, each of said hammers having an impact face of a length of at least 40% of the radius of the hammer circle.

8. A materials crusher as set forth in claim 3, further comprising means for varying the angle of inclination of said upper breaker plate to control the size of material produced by the impact of material on the upper breaker plate, and means for moving the lower breaker plate toward and away from the hammer circle without varying its angle of inclination thereby to control the proportion of fine to coarse material delivered by the crusher.

References Cited in the file of this patent UNITED STATES PATENTS 904,907 Williams Nov. 24, 1908 1,643,938 Addicks Oct. 4, 1927 2,143,498 Reichert Jan. 10, 1939 2,149,571 Battey Mar. 7, 1939 2,170,407 Hartshorn Aug. 22, 1939 2,417,078 Jones Mar. 11, 1947 2,440,388 Wright Apr. 27, 1948 2,463,631 Knight Mar. 8, 1949 2,478,733 Wright Aug. 9, 1949 2,482,279 Lemmon et al. Sept. 20, 1949 2,486,421 Kessler Nov. 1, 1949 2,492,872 Knight Dec. 27, 1949 2,618,121 Tucker Nov. 18, 1952 2,764,361 Moore Sept. 25, 1956 2,973,909 Danyluke Mar. 7, 1961 FOREIGN PATENTS 662,128 Germany July 5, 1938 

